Madrid defeated Atalanta 3-1 on Tuesday to advance 4-1 on aggregate after two consecutive eliminations in the last 16, with Karim Benzema leading the way to victory after a first-half blunder by Atalanta goalkeeper Marco Sportiello, who was among the changes made by coach Gian Piero Gasperini from the 1-0 first-leg loss in Italy.
"I don't have regrets on my initial choices," Gasperini said.
"We can't afford to make mistakes and gift goals, we wanted to do better. It's a pity."
Captain Sergio Ramos and Marco Asensio sealed Madrid's victory by scoring a goal each in the second half. Atalanta's goal came from a free kick converted by Luis Muriel late in the game.
"The goal was to advance and we came out playing with ambition to try to win the match," Ramos said.
"We controlled the game and had chances to score even more."
Sportiello tried to play from his area but misplayed his shot and the ball went directly to Luka Modric, who entered the box and made a low pass for an easy goal by Benzema from near the penalty spot in the 34th minute. Sportiello had replaced Pierluigi Gollini after the first leg and had been starting in Serie A since then.
It was the 70th Champions League goal for Benzema, making him only the fifth player to reach the mark in the competition after Cristiano Ronaldo, Lionel Messi, Robert Lewandowski and Raúl González. Only Ronaldo, Messi and Lewandowski reached the milestone quicker than the French striker's 126 matches.
Atalanta was looking to make it to the last eight for the second straight season after a remarkable run in its debut in the top European club competition. It had won all of its away games in the Champions League this season, including against Liverpool and Ajax.
It often pressed up front to try to force Madrid into mistakes but with no success as the hosts were able to stay in control during most of the match at the Alfredo Di Stéfano Stadium.
Madrid had reached the semifinals or better in eight straight seasons between 2010-11 and 2017-18 before losing to Ajax in the last 16 in 2019 and to Manchester City last season.
Madrid coach Zinedine Zidane played with the 3-5-2 formation that he had been experimenting lately, with Ramos, Raphael Varane and Nacho Fernández as central defenders and Ferland Mendy and Lucas Vázquez on the flanks.
Ramos, who converted a 60th-minute penalty kick after Vinícius Júnior was fouled inside the area, left the game a few minutes later in only his second match since a long injury layoff.
Muriel pulled Atalanta closer in the 83rd but substitute Asensio re-established Madrid's two-goal lead a couple of minutes later.
Madrid was without the suspended Casemiro and the injured Eden Hazard.
Atalanta defender Remo Freuler was unavailable because of his red card in the first leg.
In Tuesday's other game, Manchester City advanced to the quarterfinals for the fourth straight season by beating Borussia Monchengladbach 2-0, to seal a 4-0 win on aggregate.